Brown himself said he wrote the playbook "from the ground up" before the season ever started. Why would he lie?
Now, was it influenced? Yes. Brown listed both Reich and McVay as influences on what he wrote, though Reich's likely would have been greater.
As far as specifics, my guess would be the lack of pre-snap motion would have been Reich's preference. Likewise, the heavy use of shotgun and certain personnel groupings. On the flipside, as I recall some analysts didn't see many of the mesh concepts and triangle read patterns that were common for Reich before.